1. Field of the Invention
The present invention relates to a two-phase glass-like carbon member suitable for forming glass-like carbon members having a thickness exceeding 5 mm. These carbon members can be used as susceptors for supporting a silicon wafer when the silicon wafer is subjected to a thermal process. This invention also relates to a method of manufacturing such a two-phase glass-like carbon member.
2. Description of the Related Art
Glass-like carbon a carbon material has highly isotropic physical properties owing to its chemical structure.
Glass-like carbon, as compared with graphite, is very hard and has a conchoidal fracture resembling that of glass. Glass-like carbon is characterized by its very low gas permeability and small carbon particle dissipation. Glass-like carbon is classified into non-graphitizing carbon, and is obtained by carbonizing a thermosetting resin, such as a furan resin, or a phenolic resin.
Glass-like carbon is resistant to heat of 2000° C. or above in an inert atmosphere, exhibits excellent corrosion resistance to hydrogen fluoride and fluorine. Therefore, glass-like carbon members have been progressively prevalently used in semiconductor device fabricating systems, particularly, in CVD systems for carrying out CVD methods (chemical vapor deposition methods) to form films, using corrosive gases and required to generate impurities scarcely.
There are two general restrictions on the manufacture of a glass-like carbon member. A first restriction requires that the thickness of the glass-like carbon member must be less than about 3 or 5 mm. The first restriction is placed because the a thermosetting resin molding breaks due to gas generation in a carbonizing process that converts the thermosetting resin molding for carbonization. Water, carbon monooxide and carbon dioxide gas are produced by the thermal decomposition of the resin in the carbonizing process. Since the gas permeability of the resin or a transient substance produced during the carbonization of the resin is not necessarily high, the thermosetting resin molding breaks due to stress induced therein by the generated gas if the thermosetting resin molding has an excessively large thickness. Therefore, the general glass-like carbon member is required to have a small thickness of less than about 3 or 5 mm and possible glass-like carbon members have been limited to disks and pipes.
A second restriction is that glass-like carbon is hard to work by grinding due to the high surface hardness and low toughness of glass-like carbon and that thermosetting resin which is a preform of glass-like carbon is poor in moldability and workability. Thus, it has been difficult to manufacture glass-like carbon members having a complicated shape at low manufacturing costs.
A first conventional technique to eliminate the first restriction is to heat and compresse a solid thermosetting resin to form a porous thermosetting resin molding, and carbonize the porous thermosetting resin molding to obtain a porous glass-like carbon member. Since this porous glass-like carbon member is obtained by carbonizing the porous thermosetting resin molding, the porous thermosetting resin molding can be carbonized without being broken by gas generation even if the thickness of the porous thermosetting resin molding is greater than about 5 mm. Since the porous thermosetting resin molding is excellent in grindability, the minute adjustment of the shape of the porous thermosetting resin molding can be easily achieved and hence a porous glass-like carbon member having a complicated shape can be obtained.
However, the porous glass-like carbon member is inferior to the dense glass-like carbon member in resistance to gas adsorption and gas permeation. The porous glass-like carbon member having a low surface hardness is liable to produce particles. Thus the porous glass-like carbon member does not satisfactorily satisfy characteristics required of the glass-like carbon member including resistance to gas adsorption, resistance to gas permeation, high surface hardness and corrosion resistance.
A second conventional technique provides a glass-like carbon-coated carbon member having a carbon base formed of, for example, graphite and a glass-like coating the carbon base (refer to JP-A 64-47019 and JP-A 10-95668 for more information). This glass-like carbon-coated carbon member is manufactured by coating a graphite base with a thermosetting resin, and carbonizing the thermosetting resin coating the graphite base to coat the graphite base with a glass-like carbon coating. Since the carbon base of this glass carbon-coated carbon member is formed of graphite, the glass-like carbon-coated carbon member can be formed in a thickness exceeding about 5 mm. Since graphite is highly workable, the glass-like carbon-coated carbon member can be formed in a complicated shape.
However, only the thermosetting resin coating the graphite base of the glass-like carbon-coated carbon member shrinks and the graphite base does not shrink during carbonization. Consequently, stress is induced in the glass-like carbon-coated carbon member due to difference in dimensional change between the graphite base and the glass-like carbon coating and, in some cases, the glass-like carbon coating falls off the graphite base. The adhesion of the glass-like carbon coating to the graphite base is insufficient due to the shrinkage of the thermosetting resin surface layer during carbonization and hence it often occurred that the glass-like carbon coating comes off the graphite base while the glass-like carbon-coated carbon member is in use. If the graphite base is not perfectly coated with the glass-like carbon coating, graphite particles and impurities are produced.